Non-coherent DP-MOK reception process with combination of multiple paths and corresponding receiver

ABSTRACT

Process for non coherent DP-MOK reception with combination of multiple paths and corresponding receiver.  
     According to the invention, demodulation of orthogonal signals (MOK) is combined with a differential phase demodulation (DP) and diversity processing related to multiple paths in the radiofrequency channel. Diversity processing is achieved making use of differential demodulation by calculating a weighting factor, this factor then being used in the MOK part (before selecting and switching) and in the DP part to correct the calculated energy.  
     Applications for digital transmissions.

TECHNICAL FIELD

[0001] The purpose of this invention is a process for non-coherentDP-MOK reception with combination of multiple paths and correspondingreceiver.

[0002] The invention has a general application in digital communicationsand more particularly in Wireless Local Area Networks (WLAN), insubscriber Wireless Local Loops (WLL), in mobile telephony, domotics andremote collection, communication in transport systems, etc.

STATE OF PRIOR ART

[0003] The invention originates from the spectrum spreading technique.It is known that this technique consists of modulation of a digitalsymbol to be transmitted using a pseudo-random sequence known to theuser. Each sequence is composed of N elements called “chips”, with aduration that is one Nth of the duration of a symbol. The result is asignal for which the spectrum is spread over a range N times wider than-the range of the original signal. On reception, demodulation consistsof correlating the received signal with the sequence used when sending,to find the original symbol.

[0004] There are many advantages with this technique:

[0005] discretion, since the power of the signal emitted is constant anddistributed in a band N times wider, its spectral power density isreduced by a factor of N;

[0006] immunity to deliberate or parasite narrow band emissions, thecorrelation operation done at the receiver producing spectrum spreadingof these emissions;

[0007] difficulty in interception (for typical signal to noise ratios)since demodulation requires knowledge of the sequence used in emission;

[0008] resistance to multiple paths which, under some conditions, cancause selective frequency fading and therefore only partially affect thetransmitted signal;

[0009] possibility of division with multiple access using Code DivisionMultiple Access (CDMA); several spectrum spreading links by directsequence may share the same frequency band by using orthogonal spreadingcodes.

[0010] But there is a disadvantage with this technique, namely its lowspectral efficiency. The spectral efficiency is the ratio between thebinary data flow and the occupied band width. If each data symbolcontains m bits, the binary data flow is equal to m times the flow insymbols, namely mDs. The occupied band is equal to twice the “chip”frequency, in other words 2N times the symbols flow, namely 2NDs.Finally the spectral efficiency is equal to the ratio$\frac{mDS}{2{NDS}},{{which}\quad {is}\quad {\frac{m}{2N}.}}$

[0011] One approach would be to increase the spectral efficiency byreducing N, but this would degrade the qualities specific to spreading,and particularly would reduce the immunity of transmissions. Anotherpossibility would be to increase the symbols flow, but the interferencephenomenon between symbols would only be aggravated.

[0012] Another solution would be to use Code Division Multiple Access(CDMA), and particularly its synchronous variant (Multi Code—CodeDivision Multiple Access—MC-CDMA). But this method also has its limitsrelated to the occurrence of multiple access interferences.

[0013] Final solution would be to increase m, the number of binary dataper symbol, that would result in the use of complex modulations calledhigher order modulation. Remember that two of these modulations arecalled the PSK or “Phase Shift Keying” modulation which is a phasemodulation (or coding) and the MOK (M-ary Orthogonal Keying) modulationof order M. A description is given in the following two general books:

[0014] Andrew J. VITERBI: “CDMA—Principles of Spread SpectrumCommunication” Addison-Wesley Wireless Communications Series, 1975,

[0015] John G. PROAKIS: “Digital Communications” McGraw-HillInternational Editions, 3^(rd) edition, 1995.

[0016] Concerning firstly phase modulation, the usual modulation type isbinary modulation denoted BPSK, or quaternary modulation denoted QPSK.For binary modulation, symbols are coded with one binary element (m=1),and for the second case the symbols are coded with two binary elements(m=2).

[0017] These modulations are usually used in their differential form(DBPSK, DQPSK), (abbreviated as “DP” in the remainder of thisdescription). This gives good robustness in difficult channels, when nophase recuperation loop is necessary. This differential form is alsovery well adapted to the processing of various propagation paths.

[0018] On reception, a differential demodulator multiplies the signal tobe demodulated and its delayed version by a symbol period. In the caseof quaternary modulation, two channel signals are used, one channel thatprocesses the signal component in phase with a carrier and anotherchannel that processes the component in quadrature with the carrier.

[0019] The MOK modulation technique associates one signal selected froma set of all orthogonal signals, with each symbol to be sent. Thesesignals may be spreading codes in the same family of orthogonal codes.In this case, the modulation also performs the spreading. But thesesignals may also be not perfectly orthogonal since the orthogonalityconstraint is not as strong as it appears. But naturally, in this caseperformances are not as good.

[0020] If a symbol is composed of m bits, there are 2^(m) possibleconfigurations for the symbols. Therefore the number M of availablecodes needs to be equal to at least M, where M=2^(m). If the length ofthese codes is N, it is known that N orthogonal codes may be found.Therefore M=N and the number of bits per symbol is limited to log₂N.

[0021] It is known that MOK receiver is illustrated in FIG. 1 attached.This figure shows a bank of adapted filters 10 ₁, 10 ₂, . . . , 10 _(M),followed by the same number of samplers 12 ₁, 12 ₂, . . . , 12 _(M),circuits 14 ₁, 14 ₂, . . . , 14 _(M) for determining the modulus or thesquare of the modulus of the sampled signal, a circuit 16 to determinethe signal with the highest modulus, in other words to determine thenumber of the channel with the highest signal, a circuit 18 that usesthis channel number to restore the code and therefore the symbol.

[0022] There is a variant to the MOK technique called MBOK (M-aryBi-Orthogonal Keying) that consists of adding the opposite of a set oforthogonal signals used in a MOK modulation to the signals, to create aset of 2M signals that are obviously no longer orthogonal with eachother. The demodulation still uses M correlators adapted to each of theM orthogonal codes, but also requires means of recuperating the sign.

[0023] If the number of binary elements m in each symbol is increased byone unit to increase the spectral efficiency, the number M of availablecodes would be doubled, which would double the number of receiverchannels. Therefore, the complexity increases much more quickly that thespectral efficiency. Therefore this technique is limited.

[0024] The MOK and MBOK modulations are used in some digitalcommunication systems in liaison with a coherent reception structure,which requires knowledge of the phase of the carrier. Sending a preamblebefore sending useful data is a conventional process used to estimatethis phase. However, in channels subject to fading and/or multiplepaths, variations that may be very fast are applied to the phase of thecarrier and the reception system must detect and compensate for thesevariations. This is usually achieved by periodically sending preamblesthat then occupy the channel and reduce the useful data flow. With thisscheme, the durations of the preamble and the useful data packet must beless than the channel coherence time (the time during which the channelis considered to be in a stationary state). Furthermore, the complexityof the reception structure is increased.

[0025] For these reasons, an expert in the subject prefers to usenon-coherent or differentially coherent demodulation schemes that do notrequire any knowledge of phase information. These techniques eliminatethe use of long preambles, phase estimators and phase derotaters, at theprice of a slight loss of sensitivity. Furthermore, non-coherentdemodulation very much simplifies the processing of the diversity ofpropagation paths since each path has its own phase (among otherproperties) and therefore requires its own phase estimator in a coherentscheme.

[0026] Receivers with spectrum spreading using a differential phase DPdemodulation are also known. FIG. 2 attached thus shows a receivercomprising an antenna 20, a local oscillator 22, a multiplier 24, anamplifier 26, an adapted filter 28, a delay line 30, a multiplier 32, anintegrator 34 and a decision circuit 36.

[0027] This receiver is based on the following operating principle.

[0028] The adapted filter 28 performs the correlation operation betweenthe received signal and the spreading sequence that was used to send thedata. The principle of differential phase modulation chosen for sendingmeans that the information is carried by the phase difference betweenthe signals at the output from the adapted filter 28 and the output fromthe delay line 30. This information is restored by the multiplier 32.

[0029] There is a correlation peak at the output from the multiplier 32,for each propagation path. The role of the integrator 34 consists oftaking account of information provided by each propagation path. Sincethe propagation paths in an environment with multiple paths arestatistically independent, this particular receiver technique uses aprocessing based on diversity, that may have a very high order when thepulse response is complex. The decision circuit 26 is used to recoverthe sent data and also to regenerate the clock.

[0030] In practice, signals can be processed as illustrated in FIG. 3attached. The receiver shown comprises two analog channels, one toprocess part I of the signal in phase with the carrier and the other toprocess part Q in quadrature with this same carrier.

[0031] Channel I comprises first adapted filter means 50 (I) capable offulfilling a first filter function corresponding to the pseudo-randomsequence used when sending; these first means output samples I_(k). Thechannel I also includes first delay means 60 (I) to perform a firstfunction to introduce a delay equal to the period Ts of the symbols andto output samples I_(k−1). The channel Q comprises second adapted filtermeans 50 (Q) capable of performing a second filter function stillcorresponding to the pseudo-random sequence; these second means outputsamples Q_(k); the channel Q also comprises second delay means 60 (Q) toperform a delay function introducing a delay equal to Ts and to outputsamples Q_(k−1).

[0032] The multiplier 70 outputs combinations of products of thesesamples and particularly a signal denoted Dot(k) that is equal toI_(k)I_(k−1)+Q_(k)Q_(k−1) and a signal denoted Cross(k) that is equal toQ_(k)I_(k−1)−I_(k)Q_(k−1). The circuit shown in FIG. 3 is used with acircuit 90 that processes the Dot(k) and Cross(k) signals and outputs aclock signal H and data D. A programming means 72 controls the completesystem.

[0033] This solution does not correct the general problem with this typeof receiver due to the fact that the demodulator output signal sometimesrepresents a signal proportional to the energy transported on a givenpropagation path (energy equal to the square of the amplitude of thereceived echo) and sometimes noise.

[0034] Therefore the simple integration processing done in a known typeof differential receiver corresponds to the sum of energy transported byall propagation paths, and also signals not representative ofpropagation paths, which deteriorates the signal to noise ratio. Inother words, this technique does not isolate correlation peaks.

[0035] However, one technique was imagined to attempt to overcome noiseexisting between correlation peaks. This is the RAKE technique. Itconsists of isolating a number of propagation paths and adding only theenergy transported by these paths. In this approach, a number of adaptedfilters (correlators) are used to sample a channel and therefore toposition the teeth of the “rake”, other correlators then being used totrack the paths with the highest energy. Processing then summates thesquares of the amplitudes of the selected paths.

[0036] Information about RAKE type architectures using a coherentmodulation can be found in the article entitled “ASIC Implementation ofa Direct-Sequence Spread-Spectrum RAKE-Receiver” by Stephen D. LINGWOOD,Hans KAUFMANN, Bruno HALLER, published in IEEE Vehicular TechnologyConference VTC'94, Stockholm, June 1994, pp 1-5.

[0037] But there are also disadvantages with this solution:

[0038] in practice, only a limited number of propagation paths can betracked (2 to 4 in practice in known embodiments); in the case of a longpulse response in which there is a large number of separate paths, theorder of diversity (in other words the number of statisticallyindependent items of information processed at the same time) is limited;not all the information transported by the transmission channel is used,

[0039] the agility of correlators used to sample the channel to put theteeth of the rake into position must be very good to be able to adapt tofast variations in the transmission channel (coherent modulation).

[0040] In an attempt to overcome these disadvantages, the nature of thesignal to be processed must be reconsidered and an attempt must be madeto imagine a satisfactory processing. In the case of a 2-stage phasemodulation called DPSK (Differential Phase Shift Keying), only theDot(k) signal needs to be analyzed to find the transmitted data. TheCross(k) signal can be used to make an automatic frequency check.

[0041] A Dot signal, if there is only one propagation path between thesender and the receiver, is composed of peaks that are sometimespositive and sometimes negative depending on the value of the binaryinformation transmitted. The interval between two consecutive peaks isequal to the duration Ts of a symbol.

[0042] In the case of a 4-stage phase modulation called DSPSK (Q forQuaternary), the two Dot and Cross signals must be examined at the sametime to find the transmitted data.

[0043] If there are several paths, the peaks are doubled, tripled,quadrupled, etc. for each symbol, the number of detected peaks beingequal to the number of paths used by the radioelectric wave between thesender and the receiver.

[0044] A simple integrator like the integrator 24 in FIG. 1 integratedin circuit 90 in FIG. 2 will integrate all signals present, in otherwords the peaks (corresponding to true information) and the noise (notcorresponding to any information). Therefore the signal to noise is low.

[0045] French patent FR-A-2 752 330 deposited by the Applicant of thispatent describes a means of overcoming this disadvantage. The signalobtained using the sum of the squares of the Dot(k) and the Cross(k)signals, and then extracting the square root of this sum, directlyreflects the energy distribution of the different propagation paths, theamplitude of each peak being the energy transported by the correspondingpath. Therefore, according to this document, the first step is tomeasure a quantity E (k) defined as follows:

E(k)=[Dot(k)²+Cross(k)²]^(½)

[0046] The next step is an operation to take the average of the energyE(k) over a few symbols, in other words a few values with rank k. Thenumber N of symbols used for this estimate of the average mustcorrespond to a duration less than the channel coherence time, in otherwords the time beyond which two distinct waves with the same origin nolonger interfere. It is assumed that the transmission channel keeps itscoherence properties for a duration equal to N times the duration Ts ofa symbol (stationarity assumption).

[0047] This average E^(moy) is then used to weight the instantaneousDot(k) and Cross(k) signals, for example by simple multiplication ofDot(k) and Cross(k) by the value E^(moy). This then gives two newsignals called weighted signals, namely Dot(k)^(moy) and Cross(k)^(moy).These weighted signals that reflect the average of the energy on severalsymbols are then used for the integration processing over a symbolperiod Ts, the clock is then regenerated and the data are retrieved.

[0048] Taking an average of the instantaneous output is a means ofkeeping the peaks corresponding to propagation paths on the Dot^(moy)and Cross^(moy) outputs (using the channel stationarity assumption onthe few symbols used) and very significantly reducing the noise levelgenerated by the electromagnetic environment, frequency sliding or phaserotation.

[0049] The advantages obtained are then as follows:

[0050] improvement of the signal to noise ratio of the Dot^(moy) andCross^(moy) outputs before the stages for integration, retrieval of theclock and restitution of the sent binary data,

[0051] use of all energy in all propagation paths (unlike RAKE typearchitectures),

[0052] simply obtaining an estimate of the pulse response of thetransmission channel with no limitation to a given number of pathsconsidered as having the highest energy.

[0053]FIG. 4 shows a receiver conform with this document. This receivercomprises means already described in FIG. 3 and that have the samenumeric references. It further comprises a circuit 100 placed betweenthe multiplier 70 and the data reproduction and clock regenerationcircuit 90. An example of this circuit 100 is illustrated in FIG. 5.This circuit comprises a circuit 110 for calculation of the energy E, acircuit 120 for calculation of the average E^(moy), and a circuit 130for weighting the Dot and Cross signals (the rank k will be omitted inthe rest of this description for simplification purposes). The circuit130 outputs signals weighted by the average, namely the Dot^(moy) andCross^(moy) weighted signals that are then applied to circuit 90.

[0054] The document mentioned shows one possible embodiment of thesecircuits (see FIG. 8 in the document).

[0055] Although this multiple path combination technique recommended indocument 2 757 330 really does result in the stated advantages, theseadvantages are related to the differential modulation DP but they do nottake advantage of the MOK modulation described above. The purpose ofthis invention is to combine these various techniques to combine theiradvantages.

PRESENTATION OF THE INVENTION

[0056] According to a first characteristic of the invention, a mixeddemodulation is used in the sense that it partly uses the MOK modulationand partly the phase differential DP modulation. Since the DP modulationis differential, the demodulation is non-coherent. Therefore some of thebits in each symbol are transmitted using the MOK technique, and some ofthe bits are transmitted using the DP technique with spectrum spreadingusing the pseudo-random sequence selected in the MOK part. In reception,the first step is to restore the pseudo-random sequence used intransmission by adapted parallel filtering, therefore retrieving some ofthe symbol bits, and the appropriate filtered signal is demodulateddifferentially to find the other part of bits. Thus, the advantagesspecific to each modulation/demodulation are retained, while increasingthe spectral efficiency.

[0057] To emphasize the mixed nature of his process, the Applicantrefers to it with the abbreviation “DP-MOK”, illustrating thedifferential nature of the phase demodulation part and its combinationwith the MOK technique.

[0058] It may be observed that this combination of the MOKmodulation/demodulation technique and the DP technique would initiallyseem to be a nonsense because in MOK demodulation, the successivesignals corresponding to the successive symbols appear on differentchannels since, in general, successive symbols are different anddifferent codes correspond to them. However in DP demodulation, a signaland the previous signal have to be processed on the same channel.Therefore, these two techniques would apparently need differentconnections. Therefore, the combination according to the firstcharacteristic of the invention requires special switching (orconnection) between the MOK part and the DP part.

[0059] According to a second characteristic of the invention, acombination of paths is made in the differential demodulation part byweighting peaks, and this weighting is used in the MOK part beforeselecting the channel with the highest energy. Therefore, processing ofdiversity is also done in the MOK part by weighting the energy of eachchannel. In other words, the transmission channel is estimated in the DPpart but the estimate is used in the DP part and in the MOK part.

[0060] It should be noted that document U.S. Pat. No. 5,692,007 alreadydescribed a receiver making use of combined phase differential (DP) andmultiple orthogonal signals (MOK) modulations. But the receiverdescribed is a simplified version of a coherent receiver in which thephase is estimated for each symbol using a table and in which thedifferential demodulation is done by subtracting the phase of twoconsecutive symbols. Therefore it is not a non-coherent reception likethis invention. Furthermore, this document does not take account ofmultiple propagation paths using a RAKE structure.

[0061] The purpose of this invention is a process for non-coherentreception of a signal with spectrum spreading and DP-MOK mixedmodulation with combination of multiple paths, characterized in that itcomprises the following operations:

[0062] A) the signal is processed in several M channels in parallel; ineach channel, the signal is filtered by a filter adapted to apseudo-random sequence specific to the channel; the energy of thefiltered signal is measured; this energy is weighted by a weightingfactor; the channel containing the weighted signal with the highestpower is determined; the number of this channel is decoded to reproducethe first information symbols (mMOK);

[0063] B) the filtered signal with the highest energy is selected, adifferential phase demodulation is made of this signal which producesmultiple correlation peaks corresponding to multiple paths; the energyof these peaks is calculated; this energy is weighted by the saidweighting factor; this weighted energy is decoded to restore the secondinformation symbols (mDP);

[0064] C) the average of the correlation peaks is taken over adetermined duration corresponding to several information symbols, thisaverage forming the said weighting factor acting on the energy of thefiltered signal in each channel and on the energy of the correlationpeaks.

[0065] Another purpose of this invention is a non-coherent receiver foruse of this process, characterized in that it comprises:

[0066] A) several M channels in parallel, each channel comprising afilter adapted to a pseudo-random sequence specific to the channel; acircuit for measuring the energy of the filtered signal; a circuit forweighting this energy by a weighting factor; means of determining thechannel that contains the weighted signal with the highest energy; a MOKdecoder receiving the number of this channel, and in response restoringthe first information symbols (mMOK);

[0067] B) means of selecting the filtered signal with the highestenergy; a differential phase demodulator which produces multiplecorrelation peaks corresponding to multiple paths; a circuit forweighting the energy of the peaks by the said weighting factor; adecoder restoring the second information symbols (mDP);

[0068] C) means of calculating the average energy of the correlationpeaks over a determined duration corresponding to several informationsymbols, this average forming the said weighting factor, the output ofthese means being connected to the weighting circuits of the variouschannels and the circuit for weighting the energy of the correlationpeaks.

BRIEF DESCRIPTION OF THE DRAWINGS

[0069]FIG. 1, already described, illustrates a MOK receiver;

[0070]FIG. 2, already described, illustrates a known receiver fordifferential spectrum spreading transmission by direct sequence;

[0071]FIG. 3, already described, illustrates a known digital circuit forprocessing I and Q signals;

[0072]FIG. 4, already described, shows the block diagram of adifferential demodulation receiver with combination of multiple paths;

[0073]FIG. 5, already described, shows the block diagram of the meansfor calculating the energy and the average and the weighting operation;

[0074]FIG. 6 illustrates the first characteristic of the inventionrelated to the mixed nature of the demodulations used (DP and MOK);

[0075]FIG. 7 illustrates the second characteristic of the inventionrelated to the weighting done in the DP part and in the MOK part;

[0076]FIG. 8 represents the binary error rate as a function of thesignal to noise ratio for several types of demodulations.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0077] The receiver shown in FIG. 6 comprises a general input Econnected to several M channels in parallel with filters 201, 202, 203,. . . , 20M adapted to pseudo-random spreading sequences used forsending, circuits 211, 212, 213, . . . , 21M calculating the power offiltered signals, a circuit 230 to determine which channel contains themost powerful filtered signal, this circuit having two outputs 231, 232,the first outputting the number of the channel containing the filteredsignal with the highest energy, a MOK decoder 250 which uses this numberto output the first data mMOK values corresponding to this particularcode.

[0078] The receiver also comprises a demultiplexer type circuit 240designed to select the filtered signal with the highest energy, thisdemultiplexer being controlled by the signal output by a second output232 from circuit 230, a differential demodulator 260 comprising meansalready described in relation to FIG. 2 ( 20, 22, 24 ) or FIG. 3 ( 60(I), 60 (Q), 70 ), and a decoder 270 capable of restoring the second mDPdata transmitted by this differential modulation.

[0079] A circuit 280 groups these first and second data to output thesymbol transmitted with its m data where m=mMOK+mDP, onto a generaloutput S.

[0080] The receiver shown in FIG. 7 shows the receiver means in FIG. 6with the same numeric references and shows the assumed diversity means.These means comprise an assembly 265 for calculating the weightingfactor, for example this assembly comprising a circuit 110 forcalculating the energy E of the correlation peaks and a circuit 120 forcalculating the average E^(moy) of this energy shown in FIG. 5. Thisaverage energy is used in a circuit 130 to weight the signal output bycircuit 260 (for example the Dot and Cross signals) as shown in FIG. 4,and also for weighting the energy calculated by the previous circuits211, 212, 213, . . . , 21M, in weighting circuits 221, 222, 223, . . . ,22M. This weighting is done before the selection is made by circuit 230.The signals taken from each of the channels need to be suitably delayed,as shown by the delay line 235, so that switching can be done correctly.

[0081] For example, the following rules could be used to choose thevalues of mMOK and mDP:

[0082] a large value of mMOK (for example greater than 4) considerablyincreases the complexity (the increase is exponential);

[0083] a large value of mDP (for example greater than 2) quickly reducesthe robustness of the modulation in difficult environments.

[0084] Therefore, a compromise is usually necessary when choosing thesetwo parameters. For example, for codes with a length of 32 for which theDP part is quaternary (DQPSK) and for which the MOK part is done withM=8, values of m=5 and mMOK=3 and mDP=2 could be used. The resultingspectral efficiency is 0.078 bps/Hz. In conventional DQPSK, it would beequal to 0.031 bps/Hz with the same processing gain and 0.078 bps/Hzwith a processing gain corrected from 15 to 10 dB.

[0085] In terms of the binary error rate, FIG. 8 (plate 1/5) showsvariations of this BER as a function of the signal to noise ratio Eb/Noshown on the abscissa and expressed in dB. Curve A corresponds to theconventional DQPSK modulation with a speed of 1 Mbsp, curve B to MOKmodulation with M=8 at 1.5 Mbps, and finally curve C in this inventionto DP-MOK modulation with M=8 and a speed of 2.5 Mbps.

1. Process for non-coherent reception of a signal with spectrumspreading and DP-MOK mixed modulation with combination of multiplepaths, characterized in that it comprises the following operations: A)the signal is processed in several M channels in parallel; in eachchannel, the signal is filtered by a filter adapted to a pseudo-randomsequence specific to the channel; the energy of the filtered signal ismeasured; this energy is weighted by a weighting factor; the channelcontaining the weighted signal with the highest power is determined; thenumber of this channel is decoded to reproduce the first informationsymbols (mMOK); B) the filtered signal with the highest energy isselected, a differential phase demodulation is made of this signal whichproduces multiple correlation peaks corresponding to multiple paths; theenergy of these peaks is calculated; this energy is weighted by the saidweighting factor; this weighted energy is decoded to restore the secondinformation symbols (mDP); C) the average of the correlation peaks istaken over a determined duration corresponding to several informationsymbols, this average forming the said weighting factor acting on theenergy of the filtered signal in each channel and on the energy of thecorrelation peaks:
 2. Non-coherent receiver for a signal with spectrumspreading and DP-MOK mixed modulation to make use of this processaccording to claim 1, characterized in that it comprises: A) several Mchannels in parallel, each channel comprising a filter ( 201, . . . ,20M) adapted to a pseudo-random sequence specific to the channel; acircuit (211, . . . , 21M) for measuring the energy of the filteredsignal; a circuit (221, . . . , 22M) for weighting this energy by aweighting factor; means (230) of determining the channel that containsthe weighted signal with the highest energy; a MOK decoder (250)receiving the number of this channel, and in response restoring thefirst information symbols (mMOK); B) means (240) of selecting thefiltered signal with the highest energy; a differential phasedemodulator (260) which produces multiple correlation peakscorresponding to multiple paths; a circuit (130) for weighting theenergy of the peaks by the said weighting factor; a PSK decoder (270)restoring the second information symbols (mDP); C) means (265) ofcalculating the average energy of the correlation peaks over adetermined duration corresponding to several information symbols, thisaverage forming the said weighting factor, the output of these means(265) being connected to the weighting circuits (231, . . . , 22M) ofthe various channels and the circuit (130) for weighting the energy ofthe correlation peaks.